Surgical devices and methods of use

ABSTRACT

A surgical device for holding and rotating an acetabular reaming head is provided, comprising a shaft having a length which runs from a first end adapted for holding an acetabular reaming head to a second end. At least part of the shaft is divergent from the axis defined by the first and second ends of the shaft, for example the shaft may include a C-shaped divergent portion. A head held by the device can therefore access the acetabular in its true anatomical position while avoiding encroachment of the shaft on surrounding body parts.

The present invention relates to improved surgical devices and theiruses, in particular a surgical reaming device for use in the removal ofbone tissue and methods for its use. The improved reaming device isparticularly for use in reducing invasion when carrying out hipreplacement and hip resurfacing surgery.

Procedures for replacement of all or part of a patient's joint have beenin existence for a number of years. The current procedures generallyrequire large incisions to be made through the skin and underlyingtissue of the patient to allow the surgeon to access and see the jointwhile the surgery is being carried out.

For example to carry out hip replacement or hip resurfacing surgery anincision approximately 25-30 cm must be made through the skin andunderlying tissue. Such an incision allows good visibility of the jointand the surgery can therefore be carried out using the naked eye.Furthermore current surgical devices such as reaming devices, impactorsand pushers used in surgery such as hip replacement and his resurfacingrequire good access to the joint which is provided by a large incision.

Reaming devices generally comprise a rotating cutting portion situatedat the end of an elongate drive shaft and connected to a power source.Reaming devices are used in hip replacement and hip resurfacing surgeryto remove bone tissue from the acetabulum before a prosthetic acetabularcup is fitted. Pushers and impactors are used in the fitting orprosthetic joint components such as acetabular cups to the acetabulum.

Posterior access to a hip joint is usual during surgery and, as a resultto obtain sufficient access to the joint a large amount of muscle tissuemust be divided, cut through or separated from the bone to which it isanchored. This division or separation of the muscle allows the femoralhead to be moved away from the acetabulum to allow access to theacetabulum, for example with a reaming device, or to allow removal ofthe femoral head. The division or separation of muscle is essential inthe current methods for resurfacing a hip joint where the femoral headis not removed and access to the joint is therefore reduced.

Muscles such as the gluteus maximus and gluteus medius are usually cutthrough, divided or separated from the bone to which they are attachedduring hip surgery as are the tensor fascia lata and the ilio-tibialtract. Although the muscles do repair themselves following surgery therecovery period, in and out of hospital, and the amount of physiotherapyrequired is extensive. It is also possible that the muscles may neverregain the strength they had before surgery. Furthermore cutting throughmuscles can lead to a significant loss of blood and the patient mayrequire a blood transfusion.

Therefore there remains a need for surgical device and associatedmethods for their use that reduce the size of the incision required, theamount of muscle tissue cut through or separated from the bone to whichit was attached and the access required to a joint to perform surgery.

According from a first aspect the present invention provides a surgicaldevice suitable for use in hip surgery comprising a shaft having a firstend and a second end, with the shaft being adapted at the first end tobe connected to a head, wherein at least part of the length of the shaftis divergent from the axis formed between the first end and the secondend of the shaft.

Specifically, a surgical device for holding and rotating an acetabularreaming head is provided, comprising a shaft having a length which runsfrom a first end to a second end, wherein the first end is adapted forholding an acetabular reaming head, the first and second ends definingan axis which runs through these two end points, wherein at least partof the shaft is divergent from said axis, allowing a head held by thedevice to access the acetabulum in its true anatomical position whileavoiding encroachment of the shaft on surrounding body parts.

Preferably at least part of the length of the shaft is permanentlydivergent from the axis which runs through the first end and the secondend of the shaft.

Preferably the part of the length of the shaft that is divergent fromthe axis which runs through the first end and the second end of theshaft is substantially C-shaped or includes a substantially C-shapedsection. Accordingly, in a preferred aspect the invention provides asurgical device for holding and rotating an acetabular reaming headcomprising a shaft having a length which runs from a first end to asecond end, wherein the first end is adapted for holding an acetabularreaming head and wherein the shaft includes a substantially C-shapedportion along its length.

Preferably, the part of the shaft that is divergent from the axis formsa C-shape.

In surgery such as hip resurfacing surgery the provision of asubstantially C-shaped portion or other divergent portion along thelength of the drive shaft allows a reaming head to achieve access to theacetabulum without fully anteriorly displacing the femoral head andneck. In hip resurfacing surgery this removes the head to cut throughlarge amounts of muscle tissue to allow the femoral head and neck to bedisplaced out of the acetabulum before reaming can take place.

The avoidance of the need to cut through large amounts of muscle anddisplace the femoral head and neck results in a much less invasiveapproach allowing a smaller incision through the skin and underlyingtissue to be made. The muscle damage to the patient is greatly reducedtherefore meaning that the patient can be mobilized much earlier thanwith existing resurfacing surgical methods, perhaps even on the same dayas the surgery takes place. The amount of rehabilitation time requiredin hospital is less, reducing cost and increasing patient throughout. Insome cases rehabilitation centres may be needed by patients but the timeand attention required by patients in these facilities will also be lessthan with existing surgical methods.

In hip replacement surgery the removal of the femoral head from thefemoral neck prior to reaming the acetabulum increases the access to theacetabulum when compared to resurfacing surgery. However the use of thesurgical device of the present invention facilitates reaming as itavoids encroachment of the surgical device on to the femoral shaft. Theuse of the surgical device of the present invention therefore providesthe same improvements in hip replacement surgery as it provides in hipresurfacing surgery.

The use of the surgical device of the present invention also allowsreaming to take place in the true anatomical position of the acetabulum.

The shaft of the surgical device may be any suitable drive shaft thatpermits transmission of torque. The shaft may be selected from knowntorque transmitting mechanisms and devices such as a nickel titaniumshaft, a flexible round or flat wire wound cable, a series of geardriven shafts or a series of shafts interconnected by universal joints.

Preferably, the shaft of the surgical device is connectable at the firstend to a reaming head and at the second end to a rotational driveelement. More preferably the surgical device comprises a rotatable driveshaft connectable at a first end to a reaming head and connected at asecond end to a rotational drive element.

Alternatively a rotational drive element can be positioned adjacent thefirst end of the shaft so that in use it is located between the firstend of the shaft and the reaming head.

The rotational drive element may be a manual drive element such as ahandle to turn; alternatively the drive element may be an electricalpower source. Most preferably the rotational drive element is an airpowered or battery powered rotating drive element. The drive elementmust provide high torque at a low speed for maximum efficiency.

The rotational drive element may be provided with one or more gears.

It is preferred that a section of the shaft adjacent the first end isstraight and a section of the shaft adjacent the second end is straight,and these straight sections are aligned with one another.

In a preferred embodiment the shaft has a substantially C-shaped portionand the section of the drive shaft between the substantially C-shapedportion and the first end that is connectable to the reaming head isstraight and of sufficient length to ensure that eccentric motion of thedrive shaft where it causes rotation of a reaming head is prevented. Itis however also preferred that this section is not so long that thissection encroaches on the femur or femoral shaft when in use.

Preferably the section of the drive shaft between the substantiallyC-shaped portion and the first end that is connectable to a reaming headand the section of the drive shaft between the substantially C-shapedportion and the second end are both straight. It is further preferredthat these two sections are in line with each other as this allowsaccurate guidance of the reaming head.

A protective sleeve may, preferably, surround the drive shaft. In oneembodiment, the drive shaft is held to the protective sleeve; forexample with a series of bearings, which keep the drive shaft fromriding on the inside of the housing. The protective sleeve is preferablymade from metal, most preferably stainless steel. The protective sleeveis preferably made from cannulated material. The protective sleeveshields the drive shaft from body tissue during use and also shields thebody tissue from damage by the rotating drive shaft.

The protective sleeve may comprise two or more sleeve members that areseparable from each other, e.g. to allow cleaning. Such sleeve membersmay be connected by any suitable means. For example, the drive shaft mayinclude at one end a capture mechanism adapted to receive an end of eachof the housing members and align them in the correct position, and atits other end a ring adapted to interact with a catch in one of thehousing members so as to retain the housing members in a connectedformation.

The surgical device is preferably provided with a handle, suitable formanipulation by a surgeon. The handle may be provided as part of theshaft at the end furthest from the reaming head. In a preferredembodiment the handle is formed as part of the sleeve in which the driveshaft rotates.

The surgical device may be adapted at the first end of the shaft toconnect to a reaming head by the provision of any suitable connectingmeans. The surgical device may be adapted so that the reaming head maybe connected to the sleeve of the drive shaft by any suitable connectingmeans.

One preferred connecting means is the provision of one or morespring-biased pins and corresponding apertures, one part of theconnecting means being provided on each of a neck extending from a baseof a reaming head and the sleeve of the drive shaft. Another preferredconnecting means is a bayonet mechanism, preferably with the bayonetfitting being provided on the end of the drive shaft. An alternativeconnecting means is a ball and cage mechanism.

The use of a simple connecting means allows the reaming head to beeasily removed from the surgical device, e.g. for cleaning or forexchange of the head for a different sized head.

The present invention also provides, in a second aspect, a surgicalinstrument for acetabular reaming comprising a surgical device of thefirst aspect, as defined above, and an acetabular reaming head; whereinthe acetabular reaming head is attached to the first end of the surgicaldevice.

The reaming head can be any suitable reaming head depending on the useand the patient; a cheese grater type of reaming head is most preferred.This type of reaming head collects reamed material within the reaminghead. Generally a number of reaming heads will be used in successionbeginning with a small size and increasing in size until a sufficientamount of material has been removed for an acetabular cup to be fitted.

The reaming head may be connected to the surgical device, in particularto the sleeve of the drive shaft, by any suitable connecting means, suchas those discussed above.

The base of the reaming head may suitably be detachable from the cuttingportion of the reaming head to enable the reaming head to be emptiedafter use. The base of the reaming head may be attached to the cuttingportion by any conventional means.

The use of a simple connecting means allows the instrument to be easilytaken apart, e.g. for cleaning.

Accordingly, in one embodiment a surgical instrument suitable foracetabular reaming is provided comprising a shaft having a first and asecond end, with the shaft being connected at the first end to a head,and with the first and second ends defining an axis which runs throughthese two end points, wherein at least part of the shaft is divergentfrom said axis, allowing the head to access the acetabulum in its trueanatomical position while avoiding encroachment of the shaft onsurrounding body parts.

Preferably, the part of the shaft that is divergent from the axis issubstantially C-shaped or includes a substantially C-shaped section.

The surgical instrument provided may be a reaming instrument comprisinga shaft connected at a first end to a reaming head, with at least partof the length of the shaft being divergent from the axis formed betweenthe first end and the second end of the shaft, and with the reaming headbeing connected to a rotational drive element.

It is preferred that the shaft of the reaming instrument includes asubstantially C-shaped portion along its length.

Preferably, the reaming instrument comprises a rotatable drive shaftconnected at a first end to the reaming head and connected at a secondend to a rotational drive element.

In a third aspect the invention provides a kit for performing hipsurgery on a patient, comprising a surgical device in accordance withthe first aspect described above; and one or more acetabular reamingheads having selected sizes, each operable with the first end of thesurgical device for shaping the acetabular cavity of the patient.

The kit is preferably adapted in perform hip re-surfacing surgery.

Preferably, the kit further comprises one or more acetabular cupprostheses, selectable for implantation into the prepared cavity.

In accordance with the present invention a surgical instrument may alsobe provided which is a pusher suitable for pressurising a cementedacetabular cup into position in an acetabulum. The pusher comprises ashaft having a length and being connected at a first end to a pusherhead, with at least part of the length of the shaft being divergent fromthe axis formed between the first end and the second end of the shaft.Preferably, a substantially C-shaped portion is included along thelength of the shaft.

A pusher is used to push a cemented acetabular cup into a preparedacetabulum and hold it in place under manual pressure until the cementhas cured.

The pusher head and shaft may be integral or alternatively the head maybe secured to the shaft by any of the connection means set out above orby any other suitable means. The head is preferably made from a suitablematerial, such as metal or plastic material. The shaft is preferablyrigid and is also preferably provided with a handle at the end furtherfrom the head.

The kit may therefore also suitably comprise a pusher as describedabove. Specifically, the kit may further comprise a pusher comprising ashaft having a length which runs from a first, insertion end adapted forholding a selected prosthesis, to a second end, the first and secondends defining an axis which runs through these two end points, whereinat least part of the shaft is divergent from said axis.

In accordance with the present invention a surgical instrument may alsobe provided which is an impactor suitable for use in impacting anuncemented acetabular cup into position in an acetabulum. The impactorcomprises a shaft having a length and being connected at a first end toan impactor head, with at least part of the length of the shaft beingdivergent from the axis formed between the first end and the second endof the shaft. Preferably, a substantially C-shaped portion is includedalong the length of the shaft.

An impactor is used to impact an uncemented acetabular cup into aprepared acetabulum using force applied to the free end of the shaft.

The impactor head may be secured to the shaft by any of the connectionmeans set out above, for example by means of a universal connector, orby any other suitable means. Alternatively, the impactor head and shaftmay be intergral. The head is preferably made from a suitable material,such as metal or plastic material and is preferably provided with meansto secure it to the acetabular cup during impacting.

The shaft is preferably rigid. The shaft is also preferably providedwith a handle at the end furthest from the head.

The kit may therefore also suitably comprise an impactor as describedabove. Specifically, the kit may further comprise an impactor comprisinga shaft having a length which runs from a first, impaction end adaptedfor holding a selected prosthesis, to a second end, the first and secondends defining an axis which runs through these two end points, whereinat least part of the shaft is divergent from said axis.

It is clearly preferred that for any pusher or impactor instruments usedthe section of the shaft between the substantially C-shaped portion andthe first end of the shaft is straight. It is also preferred that thissection is relatively short, such that this section does not encroach onthe femur or femoral shaft when in use. Preferably the section of theshaft between the substantially C-shaped portion and the first end ofthe shaft and the section of the shaft between the substantiallyC-shaped portion and the second end of the shaft are both straight. Itis further preferred that these two sections are in line with each otheras this allows for accurate guidance.

It is also preferred that at least part of the length of the shaft ofany pusher or impactor instruments used is permanently divergent fromthe axis which runs through the first end and the second end of theshaft.

The provision of a substantially C-shaped portion or other divergentportion along the length of the shaft of such pusher or impactorinstruments allows access of the head of the surgical device to theacetabulum without full anterior displacement of the femoral head andneck to assist in the fitting of an acetabular cup.

In a fourth aspect a surgical instrument is provided which is anosteophyte remover suitable for use in removing peripheral acetabulumosteophytes. The osteophyte remover comprises a shaft connected at afirst end to an osteophyte remover head, with at least part of thelength of the shaft being divergent from the axis formed between thefirst end and the second end of the shaft. Preferably, a substantiallyC-shaped portion is included along the length of the shaft.

Accordingly, the invention provides an osteophyte remover instrument foruse in removing peripheral acetabulum osteophytes comprising a shafthaving a first and a second end, with the shaft being connected at thefirst end to an osteophyte remover head, with the first and second endsdefining an axis which runs through these two and points, wherein atleast part of the shaft is divergent from said axis, allowing the headto access the acetabulum in its true anatomical position while avoidingencroachment of the shaft on surrounding body parts. Preferably, thepart of the shaft that is divergent from the axis is substantiallyC-shaped or includes a substantially C-shaped section. More preferably,the part of the shaft that is divergent from the axis is a C-shape.

Preferably at least part of the length of the shaft is permanentlydivergent from the axis which runs through the first end and the secondend of the shaft.

It is preferred that the section of the shaft between the substantiallyC-shaped portion and the first end of the shaft, which is connected tothe osteophyte remover head, is straight. It is also preferred that thissection is relatively short, such that this section does not encroach onthe femur or femoral shaft when in use.

The osteophyte remover head may be any head suitable for removingperipheral osteophytes. Preferably the head comprises a hemisphericalportion and a disc portion, with the hemispherical portion having asmaller radius than the disc portion. The hemispherical portion islocated centrally on one face of the disc portion such that a section ofthe face is left exposed around the hemispherical portion, said sectionhaving substantially uniform width.

The hemispherical portion is preferably releasably secured to the discportion. The hemispherical portion may suitably be secured to the discportion by means of a screw, for example the hemispherical portion maybe provided with a screw in the centre of its base, and the disc portionprovided with a correspondingly shaped threaded hole in the centre ofone face to allow the hemispherical portion to be screwed into the discportion.

Preferably the hemispherical portion is smooth and has the same radiusas the cavity that has been reamed. The disc portion is provided with aserrated section for removing peripheral osteophytes. It is preferredthat a serrated section is provided on at least part of, and preferablymost of, the area of the face to which the hemispherical portion issecured which is not covered by the hemispherical portion. However, asmooth section is preferably provided around the periphery of the face,of substantially constant width. Further, the disc portion preferablyhas smooth edges.

In one embodiment, the disc portion is provided with a centrally locatedcircular serrated section on one face, with a ring shaped smooth sectionbeing provided around the circular section, extending to the edge of theface. The edges of the disc portion are smooth. A hemispherical portionhaving a radius smaller than that of the circular section is securedcentrally to said face of the disc, so as to leave a ring of serratedsurface around its periphery, with a ring of smooth surface beingprovided around the periphery of the serrated ring, extending to theedge of the face.

The peripheral osteophyte remover is preferably provided with arotational drive element for rotating the osteophyte remover head. Therotational drive element may be a manual drive element such as a handleto turn. Alternatively, the drive element may be an electrical powersource. Most preferably the rotational drive element is an air poweredor battery powered rotating drive element. The drive element mustprovide high torque at a low speed for maximum efficiency. Therotational drive element may be provided with one or more gears.

A peripheral osteophyte remover is used to remove peripheral osteophytesfrom the acetabulum after a cavity has been reamed. The remover isprovided with an osteophyte remover head comprising a hemisphericalportion having a radius approximately the same as the radius of thecavity that has been reamed, and a disc portion having a radius biggerthan the radius of the cavity that has been reamed. The osteophyteremover head is positioned in the cavity and is rotated, thus causingperipheral osteophyte to be removed by the serrated part of the discportion, whilst the smooth periphery of the disc portion prevents damageto the soft tissue. The shape of the shaft allows positioning in thetrue anatomical position, and therefore only the minimum required amountof peripheral osteophyte is removed.

The osteophyte remover head may be secured to the shaft by any of theconnection means set out above, for example by means of a universalconnector, or by any other suitable means. Alternatively, the osteophyteremover head and shaft may be integral.

A protective sleeve preferably surrounds the rotatable drive shaft. Inone embodiment, the drive shaft is held to the protective sleeve; forexample with a series of bearings, which keep the drive shaft fromriding on the inside of the housing. Most preferably the drive shaftrotates within the sleeve. The protective sleeve is preferably made frommetal, most preferably stainless steel. The protective sleeve ispreferably made from cannulated material. The protective sleeve shieldsthe drive shaft from body tissue during use and also shields the bodytissue from damage by the rotating drive shaft.

The protective sleeve may comprise two or more sleeve members that areseparable from each other, e.g. to allow cleaning. Such sleeve membersmay be connected by any suitable means. For example, the drive shaft mayinclude at one end a capture mechanism adapted to receive an end of eachof the housing members and align them in the correct position, and atits other end a ring adapted to interact with a catch in one of thehousing members so as to retain the housing members in a connectedformation.

The provision of a substantially C-shaped portion or other divergentportion along the length of the shaft of the osteophyte remover allowsaccess of the head of the surgical instrument to the acetabulum withoutfull anterior displacement of the femoral head and neck to assist in theremoval of peripheral osteophytes after reaming.

The kit of the present invention, as described above, may therefore alsosuitably comprise an osteophyte remover instrument as described above.Specifically, the kit of the present invention may further comprise anosteophyte remover instrument for use in removing peripheral acetabulumosteophytes comprising a shaft having a first and a second end, with theshaft being connected at the first end to an osteophyte remover head,with the first and second ends defining an axis which runs through thesetwo end points, wherein at least part of the shaft is divergent fromsaid axis, allowing the head to access the acetabulum in its trueanatomical position while avoiding encroachment of the shaft onsurrounding body parts.

The present invention provides, in a fifth aspect, a method forperforming hip surgery on a patient, comprising the steps of:

-   -   a) providing a surgical device for holding and rotating an        acetabular reaming head in accordance with the first aspect as        described above;    -   b) providing an acetabular reaming head and mounting the head on        the first end of the device; and    -   c) accessing the acetabulum of the patient with the surgical        device, in its anatomical position of anteversion while avoiding        encroachment on surrounding body parts, and reaming the        acetabulum with the reaming head.

It is preferred that steps a)-c) are adapted to perform a hipre-surfacing surgery.

The shaft of the device provided in step a) is preferably surrounded bya sleeve that is C-shaped where the shaft is divergent from the axis. Itis also preferred that the shaft of the device provided in step a) has adrive element coupled to the second end. In on embodiment, the shaft ofthe device provided in step a) is coupled to a drive element between thefirst end and the head.

It is preferable that the section of the shaft adjacent the first endand the section of the shaft adjacent the second end are aligned withone another. In one embodiment of the method, the femoral head isdisclosed from the acetabulum being reamed in step c).

The method for performing hip surgery on a patient, preferably comprisesthe steps of:

-   -   a) providing a surgical device for holding and rotating an        acetabular reaming head according to the first aspect of the        invention as defined above;    -   b) providing an acetabular reaming head and attaching the head        to the first end of the device;    -   c) accessing the acetabulum of the patient with the surgical        device, in its anatomical position of anteversion while avoiding        encroachment on surrounding body parts, and reaming the        acetabulum with the reaming head;    -   d) providing an acetabular prosthesis;    -   e) providing a surgical device comprising a shaft having a        length which runs from a first, securement end to a second end,        the first and second ends defining an axis which runs through        these two end points, wherein at least part of the shaft is        divergent from said axis; and    -   f) attaching the prosthesis to the securement end and delivering        the prosthesis into the acetabulum along the insertion axis        while avoiding encroachment on surrounding body parts.

In the method it is preferred that step c) further comprises making aposterior incision that splits the fibers of the gluteus maximus of thepatient, anteriorly to their insertion in the ilio-tibial tract.

In one embodiment, the device of step e) is a pusher and the prosthesisof steps e) and f) is a trial or definitive cemented component. In analternative embodiment, the device of step e) is an impactor and theprosthesis of steps e) and f) is a trial or definitive cementlesscomponent.

The present invention also provides, in a sixth aspect, a method forperforming a total hip replacement comprising the steps of:

-   -   (a) making a posterior incision;    -   (b) performing a femoral neck osteotomy;    -   (c) preparing the acetabulum to receive an acetabular cup by        reaming the acetabulum with a surgical instrument for acetabular        reaming according to the second aspect of the invention as        defined above;    -   (d) securing an acetabular cup in the acetabulum;    -   (e) preparing the femur to receive a femoral stem; and    -   (f) securing a femoral stem to the femur.

Using the surgical instruments of the present invention in a total hipreplacement avoids the possibility of the instrument encroaching on theshaft of the femur.

Preferably, in step (d) a device is used comprising a shaft having alength which runs from a first end adapted for holding an acetabularcup, to a second end, the first and second ends defining an axis whichruns through these two end points, wherein at least part of the shaft isdivergent from said axis. For example, an instrument such as a pusher asdescribed above or an impactor as described above may be used.

The present invention further provides, in a seventh aspect, a methodfor resurfacing a hip joint comprising the steps of:

-   -   (a) making a posterior incision;    -   (b) preparing the acetabulum to receive an acetabular cup by        reaming the acetabulum with a surgical instrument for acetabular        reaming according to the second aspect of the invention as        defined above, without fully anteriorly displacing the femoral        head; and    -   (c) securing an acetabular cup in the acetabulum.

Using the surgical instrument of the present invention in hipresurfacing avoids the possibility of the instrument encroaching on theshaft of the femur and allows access to the acetabulum without fullanterior displacement of the femur.

Preferably, in step (c) a device is used comprising a shaft having alength which runs from a first end, adapted for holding an acetabularcup, to a second end, the first and second ends defining an axis whichruns through these two end points, wherein at least part of the shaft isdivergent from said axis. For example, an instrument such as a pusher asdescribed above or an impactor as described above may be used.

Although the optimum method for carrying out hip replacement or hipresurfacing surgery according to the present invention includes the useof the surgical devices and/or instruments of the present invention itis possible to reduce invasion connected with hip surgery usingconventional equipment using a surgical technique according to thepresent invention. For maximum reduction of invasion it is preferred touse the devices and/or instruments of the present invention and thesurgical methods of the present invention.

The present invention also provides a method for performing a total hipreplacement comprising the steps of:

making a posterior incision positioned such that the fibres of thegluteus maximus are split anteriorly to their insertion in theilio-tibial tract;

performing a femoral neck osteotomy;

preparing the acetabulum to receive an acetabular cup by reaming theacetabulum;

securing an acetabular cup in the acetabulum;

preparing the femur to receive a femoral stem;

securing a femoral stem to the femur.

The present invention further provides a method for resurfacing a hipjoint comprising the steps of:

making a posterior incision positioned such that the fibres of thegluteus maximum are split anteriorly to their insertion in theilio-tibial tract;

preparing the acetabulum to receive an acetabular cup by reaming theacetabulum; and

securing an acetabular cup in the acetabulum.

The posterior incision preferably begins at a distance of Xcm down fromthe tip of the greater trochanter. Xcm is the distance from the tip ofthe greater trochanter to the point of bisection of the lateral cortexby a line down the centre of the femoral neck. The incision extends atan angle of 40-50°, most preferably 45° to the femoral shaft. Theincision preferably extends proximally and posteriorly to the femoralshaft. The incision is preferably 5 to 12 cm, for example 7 to 12 cm,more preferably 5 to 10 cm in length, for example 8 to 10 cm.

The position of the incision allows the fibres of the gluteus maximus tobe split along the incision resulting in the fibres being splitanteriorly to their insertion in the ilio-tibial tract and theilio-tibial tract is not incised.

In the replacement and resurfacing surgery the acetabular cup ispreferably fitted using the pusher and/or impactor devices as definedabove.

In the replacement and resurfacing surgery a step of removing peripheralosteophytes from the acetabulum is preferably included, after thereaming step and before the step of fitting the acetabular cup. Thisstep is preferably carried out using the peripheral osteophyte removeraccording to the fourth aspect of the invention.

The present invention also provides, in an eighth aspect, a method forremoving peripheral osteophytes from an acetabulum after a cavity hasbeen reamed in said acetabulum, comprising the steps of:

-   -   a) providing an osteophyte remover instrument for use in        removing peripheral acetabulum osteophytes according to the        fourth aspect of the invention as defined above; and    -   b) positioning the osteophyte remover head in the cavity, while        avoiding encroachment of the instrument on surrounding body        parts, and removing peripheral osteophyte from the cavity by        rotating the osteophyte remover head in the cavity.

Except where clearly indicated to the contrary by the wording used, allof the preferred and optional features of each aspect of the inventionmay be used in combination with one or more of any of the otherpreferred or optional features.

Embodiments of the invention will now be described in detail withreference to the drawings in which:

FIG. 1 shows a cross section along the length of a pusher or impactor asused in the present invention;

FIG. 2 shows a cross section along the length of a peripheral osteophyteremover according to the present invention;

FIG. 3 shows a cross section along the length of a surgical device forholding and rotating a reaming head according to the present invention;

FIG. 4 shows a cross section along the length of a surgical reaminginstrument according to the present invention;

FIG. 4 a shows an enlarged view of an area of the instrument shown inFIG. 4;

FIG. 5 shows a cross section through a human hip joint based on an APradiograph;

FIG. 6 shows a cross section through the lower part of a human bodyshowing the major muscle groups around the hip joint; and

FIG. 7 shows a cross section through the lower part of a human bodyshowing the major muscle groups around the hip joint.

DEVICES OF THE PRESENT INVENTION

FIG. 1 shows a pusher/impactor instrument as used in the presentinvention. The instrument 1 comprises a rigid, substantially C-shaped,shaft 2 having a head 3 connected to a first end 2 a of the shaft 2. Thehead 3 is connected to the shaft 2 by a tapered portion 4 of the firstend of the shaft 2 a being received in a corresponding aperture 5 in thebase 3 a of the head 3. The shaft is provided with a handle 6 at the end2 b of the shaft furthest from the head 3.

The head 3 may be any suitable head for impacting or pushing anacetabular cup (not shown) into the acetabulum of a hip joint (notshown).

FIG. 2 shows a peripheral osteophyte remover instrument according to thepresent invention. The instrument 101 comprises a shaft 102 having ahead 103 connected to a first end 102 a of the shaft 102. The driveshaft 102 is housed in a stainless steel sleeve 108 within which thedrive shaft 102 is free to rotate. The sleeve 108 has a substantiallyC-shaped portion positioned near the head 103 and a straight handleportion extending from the C-shaped portion away from the head 103. Afurther straight portion is provided extending from the substantiallyC-shaped portion towards the head 103 in line with the handle portion.

The head 103 comprises a hemispherical portion 104 and a disc portion105. The hemispherical portion 104 has a radius smaller than that of thedisc portion 105, and is located centrally on a first face of the discportion 105, being secured by means of a screw 107. A serrated section105 a is provided on the face of the disc portion 105 to which thehemispherical portion is secured, covering most of the area of said facethat is not covered by the hemispherical portion 104. However a smoothsection 105 b of substantially constant width is provided around theperiphery of the face. The disc portion 105 has smooth edges.

The first end 102 a of the drive shaft 102 is received by an adapter 106extending from the centre of the disc portion 105. The shaft 102 isprovided with a rotatable drive element (not shown) at the end 102 b ofthe shaft furthest from the head 103. The first end 102 a of the driveshaft 102 must be well secured in the adapter 106 to prevent eccentricrotation of the drive shaft at the end 102 a. The drive shaft 102 mustcause true rotation of the head 103 through adapter 106.

FIG. 3 shows a surgical device 111 for holding and rotating a reaminghead according to the present invention. The device 111 comprises arotatable drive shaft 112, which is a rotatable steel power cable,providing rotation and flexibility. The first end 112 a of the driveshaft 112 is adapted so as to be connectable to a reaming head. Thesecond end 112 b of the drive shaft 112 is provided with a drive fitting113, which is adapted to be linked to a rotary power source.

The first end 112 a connects to a reaming head by a bayonet stylemechanism. Accordingly, the first end 112 a is provided with a slide 115carrying a pin component 116 of the bayonet mechanism. The pin 116co-operates with a catch 117 provided at the end of the device 111, toform a bayonet that can capture a reaming head. This mechanism allows areaming head to be securely attached but also easily removed, either forreplacement with a different sized reaming head or for cleaning.

The drive shaft 112 is housed in a stainless steel sleeve 114 withinwhich the drive shaft 112 is free to rotate. The sleeve 114 has asubstantially C-shaped portion X positioned near the first end 112 a anda straight handle portion Y extending from the C-shaped portion awayfrom the first end 112 a. A further straight portion Z is providedextending from the substantially C-shaped portion X towards the firstend 112 a in line with the handle portion Y.

The substantially C-shaped portion X allows the reaming device 111 topass through a miniature incision in the skin without impinging on theskin and to easily access the acetabulum without the need to fullyanteriorly displace the femoral head or without encroaching on to thefemoral shaft. The straight portion Y provides a handle by which tomanoeuvre the device and the straight portion Z prevents eccentricrotation of the drive shaft where it causes rotation of a head connectedto the first and of the shaft. The straight portion Y and Z are in lineto allow accurate guidance of an attached reaming head.

FIG. 4 shows a surgical reaming instrument 11 according to the presentinvention. The instrument 11 comprises a rotatable drive shaft 12, whichis a rotatable steel power cable, providing rotation and flexibility.The instrument 11 also comprises a head 13, which is connected to afirst end 12 a of the drive shaft 12. The head 13 comprises a baseportion 13 a and a cutting portion 13 b. A rotatable drive element (notshown) is connected to the second end 12 b of the drive shaft 12.

The drive shaft 12 is housed in a stainless steel sleeve 14 within whichthe drive shaft 12 is free to rotate. The sleeve 14 has a substantiallyC-shaped portion A positioned near the head 13 and a straight handleportion B extending from the C-shaped portion away from the head 13. Afurther straight portion C is provided extending from the substantiallyC-shaped portion A towards the head 13 in line with the handle portionB.

The substantially C-shaped portion A allows easy access of the reaminginstrument 11 to the acetabulum without the need to fully anteriorlydisplace the femoral head or without encroaching on to the femoralshaft. The straight portion B provides a handle by which to manoeuvrethe instrument and the straight portion C prevents eccentric rotation ofthe drive shaft where it causes rotation of the head 13. The straightportions B and C are in line to allow accurate guidance of the head 13.

The first end 12 a of the drive shaft 12 is received by a neck 15extending from the centre of the base 13 a of the reaming head 13. Thefirst end 12 a of the drive shaft 12 must be well secured in the neck 15to prevent eccentric rotation of the drive shaft at the end 12 a. Thedrive shaft 12 must cause true rotation of the head 13 through neck 15.

The neck 15 is provided with a freely rotating collar 16 held inposition around the neck 15 by two further collars 17 a, 17 b fixedlyattached to the neck 15 (see FIG. 4 a). Bearing surfaces are providedbetween the neck 15 and the collar 16. The head 13 is secured to thesleeve 14 by means of a spring-biased lug 18 on the collar 16 beingreceived within a corresponding aperture 19 provided through the sleeve14. The lug and aperture lock the collar 16 in a fixed position withinthe sleeve 14, within which the neck 15 is free to rotate. The lug 18can be disengaged from the aperture 19 by applying pressure through theaperture on to the lug against the action of the spring.

The second end 12 b of the drive shaft is connected to a first end 20 aof a connector 20. The drive shaft 12 is secured to the connector 20such that eccentric rotation is prevented. The connector 20 is providedwith an externally screw thread portion 21 at the second end 20 b. Theconnector 20 is secured by the external screw threaded portion 21 to aninternally screw threaded connector 22 for connection to an air powereddrive element (not shown) suitable for providing high torque at a lowspeed. The connector 22 is sized to fit partially into the sleeve 14 andhas a bearing surface to allow it to rotate within the sleeve 14. Grubscrews 23 can be used to further secure the connector 22 in positionwith respect to drive shaft 12.

The cutting portion 13 b can be any suitable cutting portion for areaming head depending on the patient and the required result, forexample suitable cutting portions are cheese grater cutting portions fora reaming head. The cutting portion 13 b is secured to the base 13 a ofthe head 13 by means of a fixed projection 24 and a spring-biasedprojection 25 situated diametrically opposite each other around the rimof base 13 a engaging corresponding apertures on the rim of the cuttingportion. The spring-based projection 25 can be retracted into the base13 a by means of lever 26. This is a standard fixing mechanism for acutting portion of a reaming head to be secured to the base.

The reaming instrument 11 is assembled by feeding the drive shaft 12into the sleeve 14 with the connector 20 being fed through first.Aperture may be provided on the bends of the sleeve 14 to allow the useof a poker to help the connector 20 pass round the bends in the sleeve14. The neck 15 of the head 13 is secured into a first end of the sleeve14 by means of the spring-biased lug 18. The connector 22 is secured tothe connector 20 by means of the corresponding screw threads and thegrub screws 23. The connector 22 is then secured to a rotatable driveelement and an appropriate reaming head is secured to the base 13 a.

In use the power source causes rotation of the connectors 22 and 20 andof the drive shaft 12 within the protective sleeve 14. This actionresults in rotation of the neck 15 and the attached reaming head aboutan axis X extending longitudinally through the straight portions C andB. The neck 15, the connector 20 and the straight portions C and B ofthe sleeve 21 ensure that true rotation is transmitted along the lengthof the drive shaft 12 from the power source to the head 13.

Methods for Carrying out Hip Surgery using the Devices of the PresentInvention

1) Pre-Operative Planning

From a plain AP radiograph of the patient's hip joint (shown in FIG. 5)a line is drawn down the centre of the femoral neck 19 to bisect thelateral cortex 20 of the femur 21 at a point 23 usually just below thegreater trochanter 22. The distance (x cm) from this point of bisection23 to the tip of the greater trochanter is measured (usually 5-8 cm withaverage of 6 or 7 cm).

2) Technique

Anaesthetic

General or spinal anaesthetic with 3 in 1 femoral nerve block using 30ml of plain 0.25% Bupuvicane.

Position

True lateral position

Incision

FIG. 6 shows the main muscle groups around the hip joint which are thegluteus maximus 25, the ilio-tibial tract 26, the tensor fascia lata 27and the gluteus medius 28. Using a sterile marker pen, the position ofthe greater trochanter 22 is marked and using a ruler point ‘x’ ismarked on the skin x cm (usually 6 or 7 cm) distal to the greatertrochanter tip to locate the mid femoral neck line bisection point 23 onthe femur. Skin incision 24 is started from the posterior border of thefemur at the point ‘x’ going proximally and posteriorly at an angle of45° to the femoral shaft 21 for 8-10 cm. The incision 24 will be in linewith the fibres of the gluteus maximus 25. The subcutaneous tissue isincised along this line and the fibres of gluteus maximus 25 are splitalong the whole length of the incision 24. The gluteus maximus fibres 25are split anteriorly to their insertion to ilio-tibial tract 26 and theilio-tibial tract 26 is not incised at all.

FIG. 7 shows the main muscle groups around the hip joint which are thegluteus maximus 25, the ilio-tibial tract 26, the tensor fascia lata 27and the gluteus medius 28. In a variation of the method described inrelation to FIG. 6, using a sterile marker pen, the position of thegreater trochanter 22 is marked and using a ruler point ‘x’ is marked onthe skin x cm (usually 6 or 7 cm) distal to the greater trochanter tipto locate the mid femoral neck line bisection point 23 on the femur.Skin line 24′ is marked from point ‘x’ going proximally and posteriorlyat an angle of 45° to the femoral shaft 21. A skin incision is madealong the line 24′. The skin incision is started 4 cms posterior to theposterior border of femur 21 along line 24′ and extended along this linegiving an initial incision of 5 cm. The incision along line 24′ will bein line with the fibres of the gluteus maximus 25. The incision can beextended on either end if needed depending on the size of the patient.The subcutaneous tissue is incised along this line 24′ and the fibres ofgluteus maximus 25 are split along the whole length of the incision online 24′. The gluteus maximus fibres 25 are split anteriorly to theirinsertion to ilio-tibial tract 26 and the ilio-tibial tract 26 is notincised at all.

Minimal bleeding occurs in these approaches as the incision is at thewatershed of the superior and inferior gluteal vessels. The gluteusmaximus muscle is retracted at right angles to its fibres and adiposetissue overlying the short external rotators of the hip will be exposed.The adipose tissue is cleared to expose the short external rotators ofthe hip. Thorough haemostasis is carried out of the vessles around theinsertion of the short external rotators. The pirlformis, inferior andsuperior gemalli are divided at their insertion and a stay sutureapplied to the cut ends. Retraction of the short external rotatorsposteriorly will prevent injury to the sciatic nerve. The quadratusfemoris is released from its femoral insertion. This will expose theposterior capsule of the hip joint. A thorough superior, posterior andinferior capsulotomy of the hip is performed and the hip dislocated.With forceful internal rotation of the hip, it is possible to carry outanterior capsulotomy of the joint. Flexion of the knee to 90° will allowrelaxation of the ilio-tibial tract 26. Note that in internal rotationthe split gluteus maximus fibres 25 will tend to ‘snap shut’.

3a) For Total Hip Replacement Arthroplasty

Femoral neck osteotomy is performed. This will allow easy access to theacetabulum. Further completion of circumferential capsulotomy is carriedout. Release of capsule is then performed. A Homan retractor is insertedsupero-anteriorly to the acetabulum and the femur displaced anteriorly.A Styles nail is inserted into the ischium, just posterior to theacetabular rim. Another Homan retractor is inserted inferiorlyperipheral to the transverse ligament for tissue retraction inferiorly.This will give a good access to the acetabulum. Acetabular reaming inits anatomical position of anteversion is facilitated with thesubstantially C-shaped reaming instrument of the present invention asthere will not be any encroachment of the reaming instrument drive shaftto the femur. The acetabular preparation is completed and the cementedor uncemented component is secured in the usual manner. A substantiallyC-shaped pusher is used to pressurize the acetabular component for thecemented component, alternatively a substantially C-shaped impactor isused to impact an uncemented acetabular component. Once the acetabularcomponent is secured, peripheral acetabular osteophytes are removed. Thefemur is prepared next. To allow easy access to the femoral shaft thehip is flexed to 45°, internally rotated by 90° and adducted by 30-40°to allow delivery of the osteotomised base of femoral neck. The femur isprepared and the trial femoral component is inserted. The hip is reducedand checked for stability. A definitive femoral component iscemented/inserted.

Closure

The short external rotators and quadratus femoris muscles are suturedback on to the femur. A drain is inserted in the wound and broughtproximally. The gluteus maximus fascia is closed over the drain. Ifnecessary a second drain can be inserted in the fatty layer and thewound closed in layers.

3b) For Hip Resurfacing

In view of the fact that the gluteus maximus tends to ‘snap shut’ theanterior hip capsulotomy is carried out with alternate retraction ofproximal and distal aspect of the gluteus maximus split. The hip can beput in extremes of internal rotation, adduction and flexion to allow‘delivery’ of the femoral head into the wound. Usually the femoral headcan be delivered into the wound at 90° of internal rotation, 45° offlexion and as much adduction as possible. Partial release of gluteusmaximus insertion to the femur may be required in larger patients. Thefemoral head and neck are measured for sizing of femoral head component.The femoral head guide wire is inserted with the centralising femoralhead jig. The femoral head cuts are completed in the usual manner up tothe stage ready to implant the femoral component. Any femoral head bonegrafting or cementing holes are not done at this stage. With the overallsize of the femoral head reduced at this stage the femoral head caneasily be displaced to lie deep to the gluteus medius with the hip inneutral position. This will allow further thorough anterior capsularrelease to be carried out. With the femur in a more neutral position thegluteus maximus will be relaxed. A supero-anterior Homan retractor, aStyles nail in the ischium and a Homan retractor inferiorly will giveadequate exposure to the acetabulum. As gluteus maximus insertion to thefemur is not released in most patients, displacement anteriorly of thefemur is not fully possible. For this reason normal acetabular reamingdevices cannot be used as they will not allow reaming in the anatomicalanteversion position of the acetabulum. Therefore the substantiallyC-shaped reaming instrument is used to ream the acetabulum. Thesubstantially C-shaped part of the reaming instrument will allow reamingin the true anatomical position of the acetabulum. The acetabular trialshaft will also have a substantially C-shaped configuration and also thedefinitive insertor of the acetabular component will have asubstantially C-shaped configuration to allow impaction of theacetabular component. After completion of the trial acetabular componentthe definitive acetabular component is impacted into position. Allperipheral acetabular osteophytes can be removed at this stage. TheStyles nail is removed and all the Homan retractors are removed. The hipis internally rotated to 90°, flexed to 45° and adducted to allowdelivery of the femoral head. A 3 mm vent drill hole is made into thelesser trochanter to vent the femur. A drainage cannula is inserted intothe vent hole in the lesser trochanter and connected to suction. Thefemoral neck is surrounded with a split swab or special drapes and finalpreparation of the femoral head is carried out including femoral headgrafting or drilling of the femoral head drill holes for cementation.The femoral head is dried and the definitive femoral component iscemented. All excess cement is cleared and the hip reduced. Routineclosure of the wound is carried out as described above.

4) Post Operative Regime

In the immediate post-operative period a check x-ray is carried out.Adequate analgesia is maintained and after 6-8 hours the patient canstand up with a Zimmer frame. The following day the drains are removedand the patient mobilised with a Zimmer frame. The patient should beable to transfer to a step down/rehabilitation facility if thehaemoglobin check is of satisfactory level. When the patient can bedischarged from the step down facility to home environment depends onsocial circumstances and agility of the patient.

1. A surgical instrument for acetabular reaming comprising: a surgicaldevice for holding and rotating an acetabular reaming head comprising adrive shaft having a length which runs from a first end to a second end,wherein said shaft comprises a first straight portion, a second straightportion, and an intermediate portion between said first straight portionand said second straight portion; wherein said first straight portionand said second straight portion are in line with one another andaligned along an axis defined by a line running through said first endand said second end; wherein said intermediate portion is permanentlydivergent from said axis, thereby allowing a head held by the device toaccess the acetabulum in its true anatomical position while avoidingencroachment of the drive shaft on surrounding body parts; wherein thefirst end is adapted for holding an acetabular reaming head; and anacetabular reaming head; wherein the acetabular reaming head is attachedto the first end of the surgical device.
 2. The instrument of claim 1wherein the reaming head is a cheese grater type of reaming head.
 3. Theinstrument of claim 1 wherein the reaming head has a base and a cuttingportion and the base of the reaming head is detachable from the cuttingportion of the reaming head.
 4. A surgical instrument suitable foracetabular reaming comprising: a drive shaft having a first end and asecond end, said first end and said second end defining an axis passingthere through; a head connected to said drive shaft at said first end;wherein said drive shaft comprises a first straight portion, a secondstraight portion, and an intermediate portion between said firststraight portion and said second straight portion; wherein said firststraight portion and said second straight portion are aligned along saidaxis; and wherein said intermediate portion is permanently divergentfrom said axis, thereby allowing said head to access the acetabulum inits true anatomical position while avoiding encroachment of said driveshaft on surrounding body parts.
 5. The instrument of claim 4 whereinthe part of the drive shaft that is divergent from the axis issubstantially C-shaped or includes a substantially C-shaped section. 6.A kit for performing hip surgery on a patient, comprising: a) a surgicaldevice for holding and rotating an acetabular reaming head comprising adrive shaft having a length which runs from a first end to a second end,said first end and said second end defining an axis passing therethrough; wherein said first end is adapted for holding an acetabularreaming head; wherein said drive shaft comprises a first straightportion, a second straight portion, and an intermediate portion betweensaid first straight portion and said second straight portion; whereinsaid first straight portion and said second straight portion are in linewith one another and aligned along said axis; wherein said intermediateportion is permanently divergent from said axis, thereby allowing a headheld by the device to access the acetabulum in its true anatomicalposition while avoiding encroachment of the drive shaft on surroundingbody parts; and b) one or more acetabular reaming heads having selectedsizes, each operable with the first end of the surgical device forshaping the acetabular cavity of the patient.
 7. The kit of claim 6,further comprising: c) one or more acetabular cup prostheses, selectablefor implantation into the prepared cavity.
 8. The kit of claim 6,further comprising: d) a pusher instrument comprising a shaft having alength which runs from a first, insertion end adapted for holding aselected prosthesis, to a second end, the first and second ends definingan axis which runs through these two end points, wherein at least partof the shaft is divergent from said axis.
 9. The kit of claim 6, furthercomprising: e) an impactor instrument comprising a shaft having a lengthwhich runs from a first, impaction end adapted for holding a selectedprosthesis, to a second end, the first and second ends defining an axiswhich runs through these two end points, wherein at least part of theshaft is divergent from said axis.
 10. The kit of claim 6 wherein thekit is adapted to perform hip resurfacing surgery.
 11. A kit accordingto claim 6, further comprising an osteophyte remover instrument for usein removing peripheral acetabulum osteophytes comprising a shaft havinga first and a second end, with the shaft being connected at the firstend to an osteophyte remover head, with the first and second endsdefining an axis which runs through these two end points, wherein atleast part of the shaft is permanently divergent from said axis,allowing the head to access the acetabulum in its true anatomicalposition while avoiding encroachment of the shaft on surrounding bodyparts.
 12. A method for performing hip surgery on a patient, comprisingthe steps of: a) providing a surgical device for holding and rotating anacetabular reaming head comprising a drive shaft having a length whichruns from a first end to a second end, wherein the first end is adaptedfor holding an acetabular reaming head, the first and second endsdefining an axis which runs through these two end points; wherein saiddrive shaft comprises a first straight portion, a second straightportion, and an intermediate portion between said first straight portionand said second straight portion; wherein said first straight portionand said second straight portion are in line with one another andaligned along said axis; wherein said intermediate portion ispermanently divergent from said axis, thereby allowing a head held bythe device to access the acetabulum in its true anatomical positionwhile avoiding encroachment of the drive shaft on surrounding bodyparts; b) providing an acetabular reaming head and attaching the head tothe first end of the device; c) accessing the acetabulum of the patientwith the surgical device, in its anatomical position of anteversionwhile avoiding encroachment on surrounding body parts, and reaming theacetabulum with the reaming head; d) providing an acetabular prosthesis;e) providing a second surgical device comprising a second shaft having alength which runs from a first securement end to a second end, the firstand second ends of the second shaft defining a second axis which runsthrough these two end points, wherein at least part of the second shaftis divergent from said second axis; and f) attaching the prosthesis tothe securement end and delivering the prosthesis into the acetabulumalong the insertion axis while avoiding encroachment on surrounding bodyparts.
 13. The method of claim 12 wherein steps a)-c) are adapted toperform a hip re-surfacing surgery.
 14. The method of claim 12 whereinstep c) further comprises making a posterior incision that splits thefibers of the gluteus maximus of the patient, anteriorly to theirinsertion in the ilio-tibial tract.
 15. The method of claim 12 whereinthe second surgical device of step e) is a pusher and the prosthesis ofsteps e) and f) is a trial or definitive cemented component.
 16. Themethod of claim 12 wherein the second surgical device of step e) is animpactor and the prosthesis of steps e) and f) is a trial or definitivecementless component.
 17. A method for performing a total hipreplacement comprising the steps of: (a) making a posterior incision;(b) performing a femoral neck osteotomy; (c) preparing the acetabulum toreceive an acetabular cup by reaming the acetabulum with a surgicalinstrument for acetabular reaming comprising: providing a surgicaldevice for holding and rotating an acetabular reaming head comprising adrive shaft having a length which runs from a first end to a second end,wherein the first end is adapted for holding an acetabular reaming head,the first and second ends defining an axis which runs through these twoend points, wherein said drive shaft comprises a first straight portion,a second straight portion, and an intermediate portion between saidfirst straight portion and said second straight portion; wherein saidfirst straight portion and said second straight portion are in line withone another and aligned along said axis; wherein said intermediateportion is permanently divergent from said axis, thereby allowing a headheld by the device to access the acetabulum in its true anatomicalposition while avoiding encroachment of the drive shaft on surroundingbody parts; and providing an acetabular reaming head; wherein theacetabular reaming head is attached to the first end of the surgicaldevice; (d) securing an acetabular cup in the acetabulum; (e) preparingthe femur to receive a femoral stem; and (f) securing a femoral stem tothe femur.
 18. The method of claim 17 wherein in step (d) a device isused comprising a shaft having a length which runs from a first endadapted for holding an acetabular cup, to a second end, the first andsecond ends defining an axis which runs through these two end points,wherein at least part of the shaft is divergent from said axis.
 19. Amethod for resurfacing a hip joint comprising the steps of: (a) making aposterior incision; (b) preparing the acetabulum to receive anacetabular cup by reaming the acetabulum with a surgical instrument foracetabular reaming without fully anteriorly displacing the femoral head;and (c) securing an acetabular cup in the acetabulum; wherein saidsurgical instrument comprises: a surgical device for holding androtating an acetabular reaming head comprising a drive shaft having alength which runs from a first end to a second end, wherein the firstend is adapted for holding an acetabular reaming head, the first andsecond ends defining an axis which runs through these two end points;wherein said drive shaft comprises a first straight portion, a secondstraight portion, and an intermediate portion between said firststraight portion and said second straight portion; wherein said firststraight portion and said second straight portion are in line with oneanother and aligned along said axis; wherein said intermediate portionis permanently divergent from said axis, thereby allowing a head held bythe device to access the acetabulum in its true anatomical positionwhile avoiding encroachment of the drive shaft on surrounding bodyparts; and an acetabular reaming head; and wherein the acetabularreaming head is attached to the first end of the surgical device. 20.The method of claim 19 wherein in step (c) a device is used comprising ashaft having a length which runs from a first end adapted for holding anacetabular cup, to a second end, the first and second ends defining anaxis which runs through these two end points, wherein at least part ofthe shaft is divergent from said axis.
 21. An osteophyte removerinstrument for use in removing peripheral acetabulum osteophytescomprising a drive shaft having a first end and a second end, with thedrive shaft being connected at the first end to an osteophyte removerhead, wherein said first end and said second end define an axis passingthere through; wherein said drive shaft comprises a first straightportion, a second straight portion, and an intermediate portion betweensaid first straight portion and said second straight portion; whereinsaid first straight portion and said second straight portion are in linewith one another and aligned along said axis; wherein said intermediateportion is permanently divergent from said axis, thereby allowing thehead to access the acetabulum in its true anatomical position whileavoiding encroachment of the drive shaft on surrounding body parts. 22.The instrument of claim 21 wherein the part of the drive shaft that isdivergent from the axis is substantially C-shaped or includes asubstantially C-shaped section.
 23. The instrument of claim 22 whereinthe part of the drive shaft that is divergent from the axis forms aC-shape.
 24. The instrument of claim 21 wherein the drive shaft isprovided with a rotational drive element for rotating the osteophyteremover head.
 25. The instrument of claim 24 wherein the rotationaldrive element is a manual drive element, an air powered drive element ora battery powered rotating drive element.
 26. The instrument of claim 24wherein the rotational drive element is provided with one or more gears.27. A method for removing peripheral osteophytes from an acetabulumafter a cavity has been reamed in said acetabulum, comprising the stepsof: a) providing an osteophyte remover instrument for use in removingperipheral acetabulum osteophytes comprising a drive shaft having afirst end and a second end, with the drive shaft being connected at thefirst end to an osteophyte remover head; wherein said first end and saidsecond end define an axis passing there through; wherein said driveshaft comprises a first straight portion, a second straight portion, andan intermediate portion between said first straight portion and saidsecond straight portion; wherein said first straight portion and saidsecond straight portion are in line with one another and aligned alongsaid axis; wherein said intermediate portion is permanently divergentfrom said axis, thereby allowing the head to access the acetabulum inits true anatomical position while avoiding encroachment of the driveshaft on surrounding body parts; and b) positioning the osteophyteremover head in the cavity, while avoiding encroachment of theinstrument on surrounding body parts, and removing peripheral osteophytefrom the cavity by rotating the osteophyte remover head in the cavity.28. A surgical device for holding and rotating an acetabular reaminghead, said surgical device comprising: a drive shaft that permitstransmission of torque, said drive shaft having a first end adapted forholding an acetabular reaming head, and a second end; wherein said driveshaft comprises a first straight portion, a second straight portion, andan intermediate portion between said first straight portion and saidsecond straight portion; wherein said intermediate portion comprises afirst intermediate portion and a second intermediate portion; whereinsaid first intermediate portion is closer to said first straight portionthan said second intermediate portion; wherein said second intermediateportion is closer to said second straight portion than said firstintermediate portion; wherein a tangent to a point along said firstintermediate portion forms a first angle with an axis defined by saidfirst straight portion, said first angle is greater than zero degreesand less than 180 degrees; wherein a tangent to a point along saidsecond intermediate portion forms a second angle with said axis, saidsecond angle equals 180 degrees minus said first angle; and wherein saidintermediate portion is permanently divergent from said axis.
 29. Thedevice of claim 28 wherein said drive shaft comprises a series of shaftsinterconnected by universal joints.
 30. A surgical device for holdingand rotating an acetabular reaming head, said surgical devicecomprising: a drive shaft that permits transmission of torque, saiddrive shaft having a first end adapted for holding an acetabular reaminghead, and a second end; wherein said drive shaft comprises a firststraight portion, a second straight portion, and an intermediate portionbetween said first straight portion and said second straight portion;wherein said intermediate portion comprises a first intermediate portionand a second intermediate portion; wherein said first intermediateportion is closer to said first straight portion than said secondintermediate portion; wherein said second intermediate portion is closerto said second straight portion than said first intermediate portion;and wherein said a first intermediate portion bends out of alignmentwith said first straight portion; wherein said second intermediateportion bends towards alignment with said first straight portion; andwherein said intermediate portion is permanently divergent from an axisdefined by said first straight portion.
 31. The device of claim 30wherein said drive shaft comprises a series of shafts interconnected byuniversal joints.
 32. A method for performing hip surgery on a patient,comprising the steps of: providing a surgical device for holding androtating an acetabular reaming head comprising a drive shaft having alength which runs from a first end to a second end, wherein the firstend is adapted for holding an acetabular reaming head, the first andsecond ends defining an axis which runs through these two end points,wherein at least part of the drive shaft is permanently divergent fromsaid axis, allowing a head held by the device to access the acetabulumin its true anatomical position while avoiding encroachment of the driveshaft on surrounding body parts; providing an acetabular reaming head;mounting the acetabular reaming head on the first end of the surgicaldevice; and partially anteriorly displacing the femoral head so that thefemoral head is not fully anteriorly displaced; and while said femoralhead is partially anteriorly displaced, accessing the acetabulum of thepatient with the surgical device and reaming the acetabulum with thereaming head.
 33. The method of claim 32 further comprising making aposterior incision that splits the fibers of the gluteus maximus of thepatient anteriorly to their insertion in the ilio-tibial tract.
 34. Themethod of claim 33 wherein said posterior incision begins at a startdistance down from the tip of the greater trochanter, wherein said startdistance is equal to a distance from the tip of the greater trochanterto a point of bisection of the lateral cortex.
 35. The method of claim33 wherein said posterior incision extends at an angle of forty to fiftydegrees relative to the femoral shaft.
 36. The method of claim 33wherein said posterior incision extends between five and twelvecentimeters.
 37. The method of claim 33 wherein said posterior incisionextends proximally and posteriorly relative to the femoral shaft. 38.The method of claim 32 limited to not incising the ilio-tibial tract.39. A method for performing hip surgery on a patient, comprising thesteps of: providing a surgical device for holding and rotating anacetabular reaming head comprising a drive shaft having a length whichruns from a first end to a second end, wherein the first end is adaptedfor holding an acetabular reaming head, the first and second endsdefining an axis which runs through these two end points, wherein atleast part of the drive shaft is permanently divergent from said axis,allowing a head held by the device to access the acetabulum in its trueanatomical position while avoiding encroachment of the drive shaft onsurrounding body parts; providing an acetabular reaming head; mountingthe acetabular reaming head on the first end of the surgical device; andpartially displacing the femoral head so that the femoral head is notfully displaced; and while said femoral head is partially displaced,accessing the acetabulum of the patient with the surgical device andreaming the acetabulum with the reaming head.
 40. The method of claim 39further comprising making a posterior incision that splits the fibers ofthe gluteus maximus of the patient anteriorly to their insertion in theilio-tibial tract.
 41. The method of claim 40 wherein said posteriorincision begins at a start distance down from the tip of the greatertrochanter, wherein said start distance is equal to a distance from thetip of the greater trochanter to a point of bisection of the lateralcortex.
 42. The method of claim 40 wherein said posterior incisionextends at an angle of forty to fifty degrees relative to the femoralshaft.
 43. The method of claim 40 wherein said posterior incisionextends between five and twelve centimeters.
 44. The method of claim 40wherein said posterior incision extends proximally and posteriorlyrelative to the femoral shaft.
 45. The method of claim 39 limited to notincising the ilio-tibial tract.